<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>嵌套网页</title>
</head>
<body>
    <a href="##">空链接</a> <br>
    <iframe id="" name="" class="" src="second.html" width="600" height="700"></iframe>
    <br>
    <iframe src="first.html"></iframe>
</body>
</html>